netdev - Re: [net-next PATCH 1/1] drivers: net: dsa: qca8k: fix sgmii with some specific switch revision

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Date:   Tue, 21 Sep 2021 18:02:30 +0300
From:   "Andrey Jr. Melnikov" <temnota.am@...il.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH 1/1] drivers: net: dsa: qca8k: fix sgmii with some specific switch revision

In gmane.linux.network Ansuel Smith <ansuelsmth@...il.com> wrote:
> Enable sgmii pll, tx driver and rx chain only on switch revision 1. This
> is not needed on later revision and with qca8327 cause the sgmii
> connection to not work at all. This is a case with some router that use
> the qca8327 switch and have the cpu port 0 using a sgmii connection.
> Without this, routers with this specific configuration won't work as the
> ports won't be able to communicate with the cpu port with the result of
> no traffic.

> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>  drivers/net/dsa/qca8k.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)

> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index bda5a9bf4f52..efeed8094865 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -1227,8 +1227,14 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
>                 if (ret)
>                         return;
>  
> -               val |= QCA8K_SGMII_EN_PLL | QCA8K_SGMII_EN_RX |
> -                       QCA8K_SGMII_EN_TX | QCA8K_SGMII_EN_SD;
> +               /* SGMII PLL, TX driver and RX chain is only needed in
> +                * switch revision 1, later revision doesn't need this.
> +                */
> +               if (priv->switch_revision == 1)
> +                       val |= QCA8K_SGMII_EN_PLL | QCA8K_SGMII_EN_RX |
> +                              QCA8K_SGMII_EN_TX | QCA8K_SGMII_EN_SD;
> +               else
> +                       val |= QCA8K_SGMII_EN_SD;
maybe better

+               val |= QCA8K_SGMII_EN_SD;
+               /* SGMII PLL, TX driver and RX chain is only needed in
+                * switch revision 1, later revision doesn't need this.
+                */
+               if (priv->switch_revision == 1)
+                       val |= QCA8K_SGMII_EN_PLL | QCA8K_SGMII_EN_RX |
+                              QCA8K_SGMII_EN_TX;

without else branch ?

>                 if (dsa_is_cpu_port(ds, port)) {
>                         /* CPU port, we're talking to the CPU MAC, be a PHY */